What Was Missing
by pbubbs
Summary: Out of the blue, a random Door Lady appeared in Fionna, BMO and Cake's room... and it looks like she stole their most precious items!
1. What Was Missing

**Alright! This is my first fanfic! I thought, since I really love Fionna and Cake, that I'd make it based off of the episode where Marceline sings "Just your Problem", since I really wish we'd get to see Marshall do it. So, I've basically taken the script from the episode and rewritten it. Here it is! Or... one chapter of it. It'll probably be, at the most, three chapters. I have to rewatch the episode a few times to get a sense of it. Hope you like!**

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The summer sun was shining brightly inside of the large, homey treehouse. It was rather quiet, though. The most that could be heard was the small, soft humming of Fionna the human, who stood crouched by their long wooden couch, eyes scanning the seemingly empty room for any sign of her two household companions.

Fionna adjusted her hat absent-mindedly, her bangs falling lazily over her right eye. "Cake? BMO?" She spoke to the empty room, wondering momentarily where the two had gone or if they were still at home, just somewhere where she couldn't see them.

Normally, Fionna would have felt rather bored being home all alone, curious about where her favorite mutated-cat-sister had run off to. But quite often lately, Fionna took her times of privacy to good use, certainly. She had quite an embarrassing secret, one she hoped her two friends would never find out, just so somehow, word wouldn't get to the person said secret was… well, kind of about.

Realizing she was alone, a small smile graced Fionna's face. One of the pointed bunny ears on her hat flopped to the side as she turned, pulling up one of the wooden cushions of the couch to reveal a large, bright, pink wad of bubble gum stuck to the bottom.

She puckered her soft pink lips, grabbing the piece of her beloved gum from the hard surface. The human laid the cushion back down and sat in it's place, smiling down at the wad in her hands, which stuck to her fingers and stretched at her touch.

Not too long ago, she'd asked her favorite Prince Gumball for a wad of his hair to please an old Tree Wizard who had sat himself atop of cake and refused to let her go did Fionna not, somehow, find him "prince hair". Though she had done as she was asked, the Tree Wizard had seen it only as a piece of bubble gum, so she had to search all over Aaa for the rest of the day to please him. At the end of the day, she had to cut off some of her own hair to give to the Tree Wizard, who was shown to be evil in the end.

She'd kept the gum because of her admiration and, maybe even small crush on the prince. Any time she was alone, she spent quality time with the prince's hair and maybe even spoke to it. Naturally, she did it alone because anyone would think she was weird. Especially the prince himself, which was absolutely why nobody could ever know she was doing it. Well, why she wished nobody could ever know. But things don't always go as planned. This was one of those times.

Slowly and silently, Cake and BMO slid from behind the couch, the two of them staring over at Fionna from behind. Both of them smiled slyly at one another, before Cake stretched her arm over to gently tap Fionna's shoulder. "Hey girl, what'chu doin'?"

Fionna's small scream of terror broke the cat and the game into laughter, and Fionna glared at the two, a soft blush on her pale cheeks as she tried in vain to hide the piece of pink sugar that she held so dear. "Dude?!"

Cake stretched from behind the couch to the seat opposite of Fionna, watching the younger girl with an amused smile. "Don't worry girl," Cake comforted, gesturing things with her hands as she spoke. "we won't tell anyone about the 'private time' you spend with your wad of Prince Gumball's hair."

The rosy color on Fionna's cheeks turned to fire, and she turned her face away from Cake and towards BMO, though still didn't meet eye contact. A smile had come across her face, an awkward and embarrassed one. Her cheeks felt hotter than they had in a while, and she gently rubbed her arm with her sticky, gum covered fingers. "You guys knew?" She asked the two, still avoiding meeting their eye. So much for keeping things a secret.

Cake seemed annoyed by such a question, maybe even a little offended. Her gaze became stone cold and firm. "Fionna, we're room mates." She reminded, and stepped from the couch, swaying her tail side-to-side while she gazed down at her younger sister. "Which is why I'm going to share _my _beloved keepsake with _you._"

The feline stepped away, slipping her paw under one of the treehouse's many floorboards. She pulled it up to reveal a small, blue blanket underneath, which she held with care, face softening as she rubbed it against her cheek. "Buh, buh, baduh! My old baby blanket!" She declared, treating the old and stained fabric with care despite how beaten down the poor thing looked.

Suddenly, a strange, red door unfolded itself from thin air and appeared in the room. Fionna sat up, eyebrows lifted from curiosity, stepping a bit closer to the strange door. Out of it, popped a large yellow woman, who had a hat with a door on it atop her head. She hummed excitedly, and Fionna blinked at the strange creature. "Who're you?"

The woman simply hummed in response, jumping from the door and landing beside Cake. She punched Cake across the room and swiped the blanket from her hands, causing Fionna to hold her fist up threateningly, growling at the Door Lady. She walked a few steps closer, swiping Fionna's precious wad of gum and BMO's treasured controller, causing the game to shriek in terror, yelling "no!" and reaching out for the electronic.

She threw a key to another part of the room, which caused now a brown door to unfold. Fionna, now determined, ran for the door as Cake grabbed BMO in her arms and hurried after him. On the other side of the door, a young cinnamon ball child from the Candy Kingdom was happily playing with her toy train, until the Door Lady ran by and stole the train from her grasp. Tears began to form in her eyes, and Cake and Fionna ran by side-by side. "I'll get your kid back, toy!" Fionna promised, jumping away as she began to cry, and the Door Lady threw another key in the air, making another door.

"That girl must do crazy squats." Cake mumbled to herself, while the three of them stood on the ground, looking up at the floral door. Cake held tightly to Fionna and BMO, stretching them up into the door. The three were surprised to find themselves in Prince Gumball's castle.

The prince was running after the yellow woman, yelling, "Get back here Door Lady!" The Door Lady yet again made another door, which she jumped through and left the Prince angry behind it. "You ass, ugh!" He said angrily, but turned to look at Fionna and Cake when they made their presence known. "Fionna?" He questioned, but Fionna brushed him off.

"Come on, Gumball!" Fionna said in a rush, already on her way after the door Lady, into Marshall Lee's livingroom. The black haired, handsome vampire was yelling from the other room, angrily trying to hit the Door Lady with his axe guitar. The Door Lady rushed off into another door, leaving it wide open, so when Marshall attempted to go after her, the sun burned his skin and made him scream in pain, kneeling on the floor until his skin had returned back to normal.

He shook his head, eyes squeezed tight while the other four watched him from afar, Gumball feeling a small twinge in his heart from the sight, though he ignored it to run back after the Door Lady again and help Marshall Lee to his feet.

"You okay?!" Fionna asked, concern laced through her tone as she spoke.

"Yeah…" Marshall replied, rubbing his forehead gently with his hand. Fionna now looked twice as determined as before, glancing to the faces of all her comrades.

"It's alright, we'll get her!" She declared, jumping through the door and landing onto the dusty colored ground with a small thump. The Door Lady ran even faster, the four on her trail again. One last time, she threw a larger key which had created a giant, odd looking door. Before anyone could do anything, she'd run through it and the doors shut quickly together, almost crushing Fionna, which caused Cake to hurriedly pull her back. "No!" She said, beating her fists on the dark brown door, looking down in shame. Why couldn't they catch her in time?!


	2. I'm Just Your Problem

**Pff, I just realized how lame this is or whatever. Especially Marshall-Lee's singing. I totally added some parts and hinted at the chemistry between Gumball and Marshall... Maybe a hint at some later fics? I really based their personalities off of their counterparts because I feel I'll portray them better... Oops. Cake's "rock 'n roll" appearance wasn't originally written in... but maybe I added it? Anyway, here this is. By the way, check out Ashetoashesjc on youtube for the cover of "I'm just your problem" that is sung here. It's my headcanon voice and also, my favorite cover! :) I'll watch the episode one more time and try to get the final update out; I pretty much finished it already, just haven't cranked out the ending yet...**

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She sighed, pressing her forehead against the wooden surface. A quiet, twinkly sort of sound could be heard. "What?" Fionna questioned, lifting her head to look up at the arched door in front of her, which began to form rough words carved into the stone in a small golden light.

"This door shall yield to no command, save for a song from a genuine band?" Fionna read, squinting her eyes as she watched the words come to a stop at the end of the arch. Marshall Lee and Gumball simply stood behind Fionna, watching wordlessly. After Fionna had read it completely, she threw her hands into the air in aggravation. "What is this gribblegrab!" She shouted, and Gumball came up behind her, an emotionless expression on his face.

"It's the door of the Door Lord, Fionna," He said, matter-of-factly, gesturing towards the large structure. "We used to lock them up, but they kept escaping… Because they're Door Lords. Or ladies… in this case." He balled his hand into a fist and beat it in the palm of the other.

Marshall Lee, who floated beside Gumball, had grabbed himself a sun hat to keep from burning from the light. He smirked at Gumball, biting the soft skin of his lip. "They keep escaping because _you _let them live." He chuckled, resulting in a growl and a glare from Gumball himself. Cake rolled her eyes at the two's behavior. They were almost always this way around each other. Fionna didn't seem to be paying attention at the moment.

"Hmm…" Fionna began to think, one hand rubbing her chin thoughtfully. "So," She began, looking back up. "The door said it would open for a genuine band. Let's try to music this door open as a quintet!" She concluded, excitedly jumping up and waving her hand to all four of her friends.

"Can I be the jerk in the band?" Cake asked, a grumpy expression coming over her face. "'Cause the jerk is an important part of the band's success. Hmph." Cake's form had changed from her normal, plump cat self to a form somewhat like a human, but curvy, with spiked hair that reminded Fionna a bit of when Marshall shaved his head on one side.

"I know how to get through this door," Marshall Lee smirked, strumming a chord on his guitar, closing his eyes to listen to the rhythm. "We're gonna lay down a chill jam, you know what I'm sayin', girl?" He asked Fionna, floating around her in a small circle. The younger of the group cheered.

"Hey, yeah, yeah yeah!" She pumped her fist into the air, while Cake searched her backpack for her violin, pulling it out with ease as Fionna had paid her little mind.

"Just keep it cool. 'Kay, Prince?" Marhsall opened one of his eyes to look down at the bubble gum pink prince, who crossed his arm and made a 'hmph' sound with his lips. Marshall continued to strum a few chords, laughing a little at the Prince's reaction.

The Prince quickly grabbed BMO, snatching them roughly and pulling the plate covering their face off in one tug. "Oh, my face!" BMO said in surprise, looking up at Gumball as he laid the machine on his lap and began to press their buttons, making the machine giggle.

"Let's see if you hacks can keep up with my raw talent!" Cake chanted, laying her bow onto her violin strings as she began to strum. "Ha!" Fionna began to beat box, waving her hands with every noise she made, while Marshall had begun to strum and sing.

Marshall always had a pretty voice, one that many people took a liking to. It was understandable, he was a handsome vampire, and even a little arrogant sometimes, which attracted others like a magnet. But he never bothered with any of them.

"La da da da da," Marshall rose into the air, strumming his guitar with care while he closed his eyes, simply listening to the music. "I'm gonna bury you in the ground, lada da da da, I'm gonna bury you with my sound," He sang, causing Gumball's expression to become a bit uncomfortable, while Fionna seemed to be enjoying it. "I'm gonna drink the red, from your pretty pink face, I'm gonna-"

"Marshall Lee, that's too distasteful!" He shrieked, a red blush crossing over his cheeks by the wording of the song, and not too much the song or singing itself. What was he meaning by those lyrics?

But what was on Marshall's mind, was what was he meaning by that statement? Furthermore, why did he always, somehow, manage to get on the candy prince's damn nerves somehow? What did he even do wrong this time? Why was he always doing something wrong? "Oh, you don't like that? Or do you just not like me?!" He snapped at the other, his expression showing he was hurt as he floated back, the tone of his voice suddenly changing from being light and airy to a bit passionate… unintentionally so, of course.

"Sorry I don't treat you like a God, is that what you want me to do?" He asked the prince, face turned away. Fionna and Cake stared, eyes wide, unmoving. "Sorry I don't treat you like you're… _perfect! _Like all your loyal subjects do, sorry I'm not made of sugar," He sang, resulting in a very obvious blush and stunned silence from Gumball, who was only blinking at him, mouth agape. "and I'm not sweet enough for you,"

Despite how the three felt about the song, the door behind them seemed to be enjoying it. The smiling mouths that covered it were glowing, smiling wider, happier.

Marshall Lee seemed to be getting angrier, maybe even teared up a little. He began to walk atop the door, strumming his guitar. "Is that why you always avoid me? I must be such an inconvenience to you, well, I'm just your problem, I'm just your problem…" He seemed to sigh, and shake his head. "It's like I'm not… even a person, am I?" He met eyes for a moment with Gumball, before turning away. "I'm just your problem…"

Momentarily, Gumball felt that sort of aching pain you get in your heart when you've been scolded after you've done something wrong, maybe even a feeling of guilt. What did that mean, anyway? He was anything but a problem, at least in that way. Fionna and cake certainly felt the same way.

"Well, I-I-I shouldn't have to justify what I do, I-I-I shouldn't have to prove anything to you," Marshall continued. "I'm sorry that I exist, I forget what landed me on your blacklist but I-I-I shouldn't have to be the one that makes up with you so,"

Fionna pointed to the glowing door, a smile on her face. "Look, the door!" She told Gumball, who took a moment to snap back to reality and stare at the door, eyebrow lifted.

"Why do I want to? Why do I want to? I don't have a clue, so why do I want to?" Marshall stared off into the distance, seeming frustrated again. "I'm sorry that it's this way, I don't know what else to say. 'Cuz I-I-I didn't mean to push all my friends away-"

He switched his gaze to the others, suddenly becoming a bit flustered. "And I-I wanna- Bury you in the ground, and drink the blood from your…? Ugh. You messed me up!" He snapped at Gumball, "Why are you looking at me like that?!"

The door then began to shrink away and frown again, and Fionna shook her head. "No everybody, don't stop now!" She yelled in the boy's direction. "The door was responding to it! To our music!" She stood back, rubbing her chin again. "I wonder what it liked. Or what was missing!"

"I know what was missing. Talent!" Cake yelled, throwing her hands in the air. "Hacks, talentless hacks, I'm out of here!"

"Yikes." Marshall Lee mumbled as Cake walked away, staring down at Fionna, his nerves now at ease.

"Maybe to be a more genuine band, we need to hang out as buds, and have a noodle break…" She reached behind her to grab out a hard, uncooked square of ramen from her bag, which she'd already gone to take a bite from. "C'mon, it'll help," She gestured it towards the boys, nodding her head with a smile.

Marshall began to float away, and Fionna frowned. "No, don't go too!"

"I'm just getting something to cook that with?" He laughed, and Fionna looked a little confused.


End file.
